1. Field of the Invention
The present invention relates to a diaphragm of centrally convex form used where pressure resistance is required.
2. Prior Art
Diaphragms are usually molded of rubber in membrane form and, where pressure resistance is required, they are reinforced by a base fabric of plain weave disposed in the rubber member.
In the case where the diaphragm is of centrally convex form, it has been common practice to mold such diaphragm of centrally convex form by setting a base fabric of plain weave and rubber in a press die or the like, and pressing the assembly.
However, since the base fabric is of plain weave, the warp and weft yarns constituting the portion of the base fabric in and around the centrally convex region are drawn toward the centrally convex region during press molding operation, resulting in variations in the density of warp and weft yarns, wrinkles, overlaps and the like, thus making the pressure-resisting strength nonuniform. As a result, some of the yarns constituting the base fabric are broken prematurely owing to repetitive vibrations, thus degrading the durability.